there were some problems with the Bristol Centuras air craft engine but these were ironed out and as it turns out these engines had one of the longest intervals between major overhauls ,how ever these engines may have been slightly more difficult to service and maintain than the conventional poppet valve radial engine .the British authorities obviously thought the 20% gain in power was worth the extra effort.A KI 84 Frank fitted with one of these engines would be superior to all allied and German contempory fighter planes

I do know the Sea Fury was active in the Korean war but didnt the sleeve valve tend to distort? Thus I believe serviceability was an issue.

Ron ,the Hawker Tempest Mk 2was used very late in the last war,mainly to distroy the v1 flying bomb sharing these duties with its sister ,the tempest Mk 5.THE Mk 2 was powered by a colossal Bristol centuras radial engine capable of producing over 3ooohorse power and because this engine used sleeve valves this engine had a smaller diameter than any convential radial of the same power.this allowed the tempest Mk2 to retain the slim lines of the Mk5 with no increase in frontal area ,so the Mk2Tempest was not only faster than redoubtable Mk5 but its air cooled engine was less vunerable to battle damage .If the Tempest Mk 2s engine could be fitted to the Hayate then this remarkable Japanese fighter would be the superior machine

Ron ,the Hawker Tempest Mk 2was used very late in the last war,mainly to distroy the v1 flying bomb sharing these duties with its sister ,the tempest Mk 5.THE Mk 2 was powered by a colossal Bristol centuras radial engine capable of producing over 3ooohorse power and because this engine used sleeve valves this engine had a smaller diameter than any convential radial of the same power.this allowed the tempest Mk2 to retain the slim lines of the Mk5 with no increase in frontal area ,so the Mk2Tempest was not only faster than redoubtable Mk5 but its air cooled engine was less vunerable to battle damage .If the Tempest Mk 2s engine could be fitted to the Hayate then this remarkable Japanese fighter would be the superior machine

The Ki 84 was tested against the Fw 190A-5 in Japan and the Focke-Wulf had quicker dive.
I say quicker instead of faster because the terminal dive speed isn't the same as dive acceleration on the way there.
I welcome more info on this.
It's like the dive of the Ki 84 being better than the Ki 100 even though the maximum terminal speed is about 497 mph Ki 84) vs 528 mph (well built Ki 100) respectively.
The strength of the plane comes into play as well as the weight, power, drag, compressibility and so on.
It's not so simple as level maximum speed.

Percy, could you elaborate please.
I believe the Mark V was the only production Tempest in WW 2 action.

the only allied fighter plale that was clearly superior to the japanese ki-84 was the hawker tempest mark 2

I ran across something about the Ki 84 from a Russian author.
I didn't realize the cylinder block had to be replaced during an engine overhaul after only a few flights! In fact EVERY flight the Ha-45 had to be cleaned and rebiult!
It's no wonder specially qualified mechanics were necessary to keep the fleet maintained and serviceable. Finally the model 11 was replace by the improved 12, then the 21, and then the 23 engine was much better but not as powerful, only 1900 hp. But high altitude was still trouble.
The turbocharged 2000 hp Ha-45Pu was too late.

Jim,
I believe so. I've seen a photo of a bare metal Frank with US insignia flying in formation with allied fighters including a Seafire. It could have been the one you speak of.

Was the captured Frank ( that was in the Phillipines) repainted in US stars and bars ??? Thanks. Jim

Good work Aaron,
Now if we only we had that much on all the fighters, Oh and of course control harmony, turn time (wing-loading doesn't tell the whole story) and deg/sec roll rate, and stall, terminal dive speed, stall recovery and dive pullout (compressibility) ...etc. Maybe the mystery keeps us digging.

Hey Ron are you still out there?
For Christmas my wife bought me the TAIC MANUAL No.1 on Japanese aircraft.
Mick Dunne, while the Frank could outclimb the average P-51D, it did not outclimb the P-51B when pushed to 75" engine boost pressure that was cleared in 1944 (about the time the Frank showed up).
For all those that are interested, the figures on the Ki.84 with the Ha.21 engine when it was properly constructed and maintained were:
2,040hp./7,940 lbs.combat weight/226sq.ft.wing area.
The following is SPEED mph/CLIMB fpm/TIME TO HEIGHT minutes:
362/4,275/S.L. 379/4,350/.8/1,000m. 389/3,890/1.65/2,000m.
389/3,570/2.6/3,000m. 388/3,590/3.65/4,000m. 414/3,610/4.6/5,000m. 426/3,350/5.7/6,000m. 427/3,250/5.8/6,098m. 426/2,870/6.8/7,000m. 416/2,280/8.25/8,000m. 403/1,720/9.6/9,000m. 387/1,175/10,000m.

Only let down by dismal production standards at the 'wrong' end of the war!

The straight leading edge of Nakajima fighters helped initial climb and entering a turn, but dive was highly prone to buffeting and control loss approaching compressibility, from the shock wave. So terminal dive didn't quite breach 500 mph (only 496 or 7). Flight stability in a dive was thus inferior to the Kawasaki Tony, both inline and radial models (Ki 61/100) which did well over 500 mph. So level maximum speed advantage doesn't always translate to dive speed performance.

They should have kept the Ha-109 motor from the Tojo and split the Frank like the USSR did with the Yak-9U.The engine was unreliable at first so the early -9U was powered by the previous motor which was mature and still reached 420 mph.
If the Frank had 2 lines of power plant maybe it would have given up 10 or 15 mph with the less powerful Ha-109 but it would have been a much needed reliable Frank while the bugs got worked out of the new unreliable one. It could replace the role of the Tojo and Oscar early by cutting back on internal fuel or cut the ammo supply respectively for the interceptor or dogfighter roles. The Frank could have twice as many produced in place of Oscars and Tojos with their deficiencies. And the Frank with the reliable Ha-109 would have no drawbacks in 1943. It could still be as fast as most any Japanese fighter and out maneuver any Allied fighter and rival the Zero in production output. And if the newer Ha-45 beast couldn't be tamed, supe-up the Ha-109 or Ha-112 (of Ki 100 fame). These reliable motors were around since before mid-war with 1500 hp. Perhaps the Ha-112 is slimmer than the Ha-109, I don't know.

The Frank was the more powerful fighter of IJA

In a confidential report listing titled COMPARATIVE PERFORMANCE AND CHARACTERISTICS REPRESENTITIVE ENEMY AND ALLIED AIRCRAFT the FRANK 1, Nakajima is listed as follows:
Engine: Nakajima Ha.45: 1970hp/S.L. 1695hp/21,000ft. Armament: 4x20mm. Range: 1795mls/156mph/359gallons of fuel.
Performance at the test weight of 7940lbs.: Climb: 3780fpm/S.L. 3290fpm/21,000ft. 10,000ft/2.7min. 20,000ft/5.8min. Service Ceiling: 39,000ft. Maximum Speed: 348mph/S.L. 422mph/21,000ft.
Due to all the problems it encountered in production, but taking into account the ingenuity of some chief mechanics in the field, IMHO it was likely the Ki.84 the Allied pilot would meet in combat would be capable of 325-350mph/S.L. and 384-425mph/20,000ft. Just an opinion though. I have read that the performance of the Ki.84 varied greatly in the field durring 1945.

The Ki.84 is the most contraversal Japanese fighter to evolve from WW2. It definitely had the potential to be a world beating contender if it hadn't been for its constant failure of exhaust stacks due to poor materials, inefficient welding and problems with the hydraulics.
According to Wright Field Report No. F-1IM-1119B-ND released in January 1947, a Ki.84-1 with the Ha.45 Model 21 engine, Serial No. 302, performance was found to be as follows: Speed: 350mph/S.L. 389/10,000ft. 412/20,000ft. 426/23,000ft. 400/30,000ft. 370/35,000ft. This was listed under Normal Fighter, Military Power.
Climb Normal Fighter: 3790fpm/S.L. and 3195fpm/20,900ft under Military Power. 3615fpm/17,900ft under W.E.P. Service Ceiling: 38,800ft. No test weight or engine power settings given.
On another official PERFORMANCE AND CHARACTORISTIC sheet 156A-2 the following performance is listed: Engine at T.O. and WEP: 1970hp/S.L. 2040hp/3000ft. 1850hp/17,900ft. The following performance is at 7,940lbs.: Speed: 369mph/S.L.
427mph/20,000ft. Climb: 4275fpm/S.L. 3615fpm/17,900ft. Maximum Range: 1,815mls/173mph/1500ft./359gallons of fuel.
These test figures are under ideal situations and using USA high grade fuel. However, quoting Richard Dunn:
" I have a copy of a translation of a captured document of unknown reliability which indicates two maximum speeds for the Ki.84-1 (light) and Ki.84-1 (improved versions). The two speeds apparently relate to the Ha 45 rating of 2000hp at 4,020ft and 1800hp. at 19,680ft: Ki.84-1 (light): 412mph and 430mph respectively. Ki.84-1 (improved): 409mph and 427mph respectively. The light version is listed at 7885lbs. and the improved is listed at 8507lbs.

It's interesting to read the first impression that U.S. pilots had of the Ki 84 'Frank'. That powerful long nose with 4 props, overhauling them to point-blank range like a thoroughbred! No toothless Oscar here. Unmistakably a Nakajima though. Survivors of those first encounters doubtless had their share of clean underwear changes afterward. It's no wonder the svelte 2,000 hp Hayate became the biggest worry to Allied airmen fighting Japan. Some later packed 30-mm cannon to compliment their 20-mm guns. At a fighting weight under 8,000 lbs, it was the most feared fighter, pound for pound. At the same time, it was long legged and tough by Japanese standards. The fastest they had and tight-turning too. Superlative design all-around, potentially.